In 70th decade last century, North American comb jelly invaded Caspian Sea and they ate plankton, fish berry and fry, which brought a big calamity to anchovy and herring breeding. In 1990, mnemiopsis, a kind of American organism, invaded Caspian Sea and swallowed a large amount of plankton causing nearly exhaustion of fish fry in Caspian Sea. In 1997, AQIS estimated that over 170 kinds of marine organisms invaded Australian water area. For example, Dinoflagellate caused a loss of 80 million USD. By entering the human foodstuff chain via mollusks they endangered the human health causing a quite long time discontinuity of Australian fishery industry. In 1996, there were 130 kinds of organisms invaded the Great Lakes in the boarder region between U. S. A and Canada. Up to the year of 2000, economic loss of 5 billion USD has inflicted. Asia EITor, Inaba is also brought to Latin America via ballast water of the ship. Invasion of foreign organisms via ballast water of ships will definitely bring disastrous destruction to the environment of Chinese offshore area and threaten the basis of sustainable development in our country's rapidly developing regions.
At present, many researchers are researching for an effective novel method to counteract the invasion of harmful organisms from ballast water of ships in order to solve the problem of regional limitation and obstacle to trade. In 1990, fishery organization of Great Lakes and international union proposed measures to decrease the invasive spread of organisms by replacing ballast water in international waters. This measure could effectively lower or hinder the invasion of foreign organisms. However, replacement of ballast water in deep sea could not effectively and completely remove all the organisms that cover a huge range of species. In 2000, IMO Protection Committee on Environment of Sea proposed “method of replacement of ballast water in deep sea (2000 meters below the sea level, farther than 200 nautical miles from shore)”. The method, however, had the drawbacks of high consumption of energy and requiring of long operating time. In 2000, Geoff Rigby et al carried out respectively the researches on heating the ballast water, respectively. Even though the method was considered to be of potential attraction, it still has drawback of long operating time, high energy consumption and in addition formation of thermal stress which would lower the safety of cruise. Many scientists used chlorine and sodium hypochlorite to treat the ballast water. In order to kill micro-organism and to ensure the chemicals homogeneously dispersed in the ballast water, excess amount of 100-500 mg/L of chlorine should be added which was scores of times of the amount used in common water treatment and as a result corrosion of facilities of cabin coating, pumps, pipes and the like would be aggravated. Further more, chlorine would react with organic matters in the ballast water forming carcinogenic organic chloride and the storage of several tons of liquid chlorine in the vessel would induce safety problem of leakage and explosion. Due to the above reasons, it is not feasible to apply this method to the treatment of ballast water. Early in 1998, Smethurst proposed to re-evaluate the feasibility of using chlorine in the treatment of ballast water. Many scientists also carried out a large amount of exploratory research works while MEPC and GloBallast were of the opinion that at the present there was not yet any effective method for on-line treatment of ballast water. Currently, available methods comprise: (1) water is replaced during cruise; (2) replacement of ballast water is carried out on shore of destinative harbor. The former has problems of safety and high consumption of energy while the latter has problems of investment by the local government, maintenance and management of harbor facilities.